Re: [PATCHv9 14/15] cec: s5p-cec: Add s5p-cec driver

[Hans Verkuil <hverkuil@xs4all.nl>]

On 10/12/2015 02:33 PM, Kamil Debski wrote:
> Hi,
> 
> On 12 October 2015 at 12:50, Hans Verkuil <hverkuil@xs4all.nl> wrote:
>> On 10/06/2015 12:32 AM, Russell King - ARM Linux wrote:
>>> On Mon, Sep 07, 2015 at 03:44:43PM +0200, Hans Verkuil wrote:
>>>> +    if (status & CEC_STATUS_TX_DONE) {
>>>> +            if (status & CEC_STATUS_TX_ERROR) {
>>>> +                    dev_dbg(cec->dev, "CEC_STATUS_TX_ERROR set\n");
>>>> +                    cec->tx = STATE_ERROR;
>>>> +            } else {
>>>> +                    dev_dbg(cec->dev, "CEC_STATUS_TX_DONE\n");
>>>> +                    cec->tx = STATE_DONE;
>>>> +            }
>>>> +            s5p_clr_pending_tx(cec);
>>>> +    }
>>>
>>> Your CEC implementation seems to be written around the idea that there
>>> are only two possible outcomes from a CEC message - "done" and "error",
>>> which get translated to:
>>
>> This code is for the Samsung exynos CEC implementation. Marek, is this all
>> that the exynos CEC hardware returns?
> 
> The possible status values that are implemented in the CEC framework
> are following:
> 
> +/* cec status field */
> +#define CEC_TX_STATUS_OK               (0)
> +#define CEC_TX_STATUS_ARB_LOST         (1 << 0)
> +#define CEC_TX_STATUS_RETRY_TIMEOUT    (1 << 1)
> +#define CEC_TX_STATUS_FEATURE_ABORT    (1 << 2)
> +#define CEC_TX_STATUS_REPLY_TIMEOUT    (1 << 3)
> +#define CEC_RX_STATUS_READY            (0)
> 
> The only two ones I could match with the Exynos CEC module status bits are
> CEC_TX_STATUS_OK and  CEC_TX_STATUS_RETRY_TIMEOUT.
> 
> The status bits in Exynos HW are:
> - Tx_Error
> - Tx_Done
> - Tx_Transferring
> - Tx_Running
> - Tx_Bytes_Transferred
> 
> - Tx_Wait
> - Tx_Sending_Status_Bit
> - Tx_Sending_Hdr_Blk
> - Tx_Sending_Data_Blk
> - Tx_Latest_Initiator
> 
> - Tx_Wait_SFT_Succ
> - Tx_Wait_SFT_New
> - Tx_Wait_SFT_Retran
> - Tx_Retrans_Cnt
> - Tx_ACK_Failed

So are these all intermediate states? And every transfer always ends with Tx_Done or
Tx_Error state?

It does look that way...

Regards,

	Hans

> 
>>
>>>
>>>> +    case STATE_DONE:
>>>> +            cec_transmit_done(cec->adap, CEC_TX_STATUS_OK);
>>>> +            cec->tx = STATE_IDLE;
>>>> +            break;
>>>> +    case STATE_ERROR:
>>>> +            cec_transmit_done(cec->adap, CEC_TX_STATUS_RETRY_TIMEOUT);
>>>> +            cec->tx = STATE_IDLE;
>>>
>>> "okay" and "retry_timeout".  So, if we have an adapter which can report
>>> (eg) a NACK, we have to report it as the obscure "retry timeout" status?
>>> Why this obscure naming - why can't we have something that uses the
>>> terminology in the spec?
>>>
>>
>> Actually, a NACK should lead to a re-transmission (up to 5 times), see CEC 7.1.
>> The assumption of the CEC framework is that this is done by the CEC adapter
>> driver, not by the framework. So if after repeated retransmissions there is
>> still no Ack, the CEC_TX_STATUS_RETRY_TIMEOUT error is returned. I could
>> change this to _MAX_RETRIES_REACHED if you prefer.
>>
>> The CEC_TX_STATUS_ macros were based on what the adv drivers support (except
>> for CEC_TX_STATUS_REPLY_TIMEOUT which is specific to the framework).
>>
>> Regards,
>>
>>         Hans
> 
> Best wishes,
> Kamil
> 

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